New Orleans—Numerous studies have shown poor adherence with preventive medications prescribed for patients with various chronic medical conditions, and now research conducted by urologists at the University of Michigan show this problem applies to patients prescribed medical prophylaxis for kidney stones.
The investigators used national pharmacy claims data from a recent 5-year period (2002-2006) to identify commercially insured adults who had one or more prescriptions filled for a thiazide, alkali citrate, or allopurinol after receiving a physician-coded diagnosis of nephrolithiasis. Medication adherence was evaluated using the validated proportion of days covered formula. Defining adherence as >80% proportion of days covered during the first 6 months after the index kidney stone claim, only 50% of the nearly 22,000 patients included in the cohort were adherent with their regimen.
While year-by-year analyses showed a trend for adherence improving over time, the overall adherence rate was still below 55% in the last year of the study.
Logistic regression analysis was also performed to evaluate patient factors associated with adherence. Not surprisingly, the results showed that being on combination therapy or having a less generous insurance plan independently predicted lower adherence. In addition, males were significantly more likely to be adherent than females as were Midwesterners compared with patients from other parts of the country.
“To our knowledge, this is the first study examining patient adherence to medication prescribed for kidney stone prevention, and the findings are important for urologists considering that non-adherence may mitigate treatment benefit or even cause harm,” said Yooni Yi, MD, urology resident at the University of Michigan, Ann Arbor, who presented the research at the AUA annual meeting in New Orleans.
More Stone Disease articles